ICTV Virus Taxonomy Profile: Nairoviridae 2024

Abstract Nairoviridae is a family for negative-sense RNA viruses with genomes of about 17.2–21.1 kb. These viruses are maintained in and/or transmitted by arthropods among birds, reptiles and mammals. Norwaviruses and orthonairoviruses can cause febrile illness in humans. Several orthonairoviruses can infect mammals, causing mild, severe and sometimes, fatal diseases. Nairovirids produce enveloped virions containing two or three single-stranded RNA segments with open reading frames that encode a nucleoprotein (N), sometimes a glycoprotein precursor (GPC), and a large (L) protein containing an RNA-directed RNA polymerase (RdRP) domain. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Nairoviridae, which is available at www.ictv.global/report/nairoviridae.


Abstract
Nairoviridae is a family for negative-sense RNA viruses with genomes of about 17.2-21.1 kb.These viruses are maintained in and/or transmitted by arthropods among birds, reptiles and mammals.Norwaviruses and orthonairoviruses can cause febrile illness in humans.Several orthonairoviruses can infect mammals, causing mild, severe and sometimes, fatal diseases.Nairovirids produce enveloped virions containing two or three single-stranded RNA segments with open reading frames that encode a nucleoprotein (N), sometimes a glycoprotein precursor (GPC), and a large (L) protein containing an RNA-directed RNA polymerase (RdRP) domain.This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Nairoviridae, which is available at www.ictv.global/report/nairoviridae.RNA genomes (Fig. 2).These RNAs encode, in the viruscomplementary sense, N (S segment), GPC (M segment), and L protein containing RdRP, helicase, and endonuclease domains (L segment).

REPLICATION
Nairovirid infection starts with virion attachment, mediated by G N and G C , to unknown cell-surface receptors and entry via the endosomal route [1].Viral fusion with the host cell results in early or late endosomal release, depending on the virus, of the virion RNP complex into the cytoplasm.This pH-dependent fusion event likely requires the previous participation of an intracellular receptor [1,2].During primary transcription, L generates uncapped antigenomic RNAs that are then capped using host cell-derived capped primers (cap snatching) [3].L and S segment-transcribed mRNAs are translated by free ribosomes.M segment-transcribed mRNA is translated by membranebound ribosomes, with the expressed GPC co-translationally and post-translationally cleaved by cellular proteases and glycosylated by cellular glycosidases to yield G N and G C and sometimes non-structural glycoproteins [4].The antigenome, synthesised by L protein, serves as a template for genomic RNA replication.Secondary transcription amplifies the synthesis of mRNAs and genome replication.During morphogenesis, G N and G C accumulate in the Golgi apparatus, modified host membranes are acquired, and virions bud into the Golgi cisternae [5,6].

RESOURCES
Full ICTV Report on the family Nairoviridae: www.ictv.
Funding information Production of this summary, the online chapter, and associated resources was supported by the Microbiology Society.This work was supported in part through the Laulima Government Solutions, LLC, prime contract with the U.S. National Institute of Allergy and Infectious Diseases (NIAID) under Contract No. HHSN272201800013C.J.H.K. performed this work as an employee of Tunnell Government Services (TGS), a subcontractor of Laulima Government Solutions, LLC, under Contract No. HHSN272201800013C.This manuscript was prepared whilst K.E. held a National Research Council (NRC) Research Associateship Awards at the Walter Reed Biosystematics Unit, through the Walter Reed Army Institute of Research, Silver Spring, MD, USA.The content of this publication should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of the Army, U.S. Department of the Navy, the U.S. Department of Defense, the U.S. Department of Health and Human Services, or of the institutions and companies affiliated with the authors.Material contained within this publication has been reviewed by the Walter Reed Army Institute of Research.There is no objection to its presentation and/or publication.

Table 1 .
Characteristics of members of the family Nairoviridae